Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
  • G01N33/54313—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals the carrier being characterised by its particulate form
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
  • G01N33/544—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals the carrier being organic
  • G01N33/545—Synthetic resin
  • G01N33/546—Synthetic resin as water suspendable particles
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
  • G01N33/544—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals the carrier being organic
  • G01N33/545—Synthetic resin
  • G01N33/547—Synthetic resin with antigen or antibody attached to the carrier via a bridging agent
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
  • G01N33/551—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals the carrier being inorganic
  • G01N33/552—Glass or silica
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
  • G01N2333/435—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans
  • G01N2333/76—Assays involving albumins other than in routine use for blocking surfaces or for anchoring haptens during immunisation
  • G01N2333/765—Serum albumin, e.g. HSA
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T436/00—Chemistry: analytical and immunological testing
  • Y10T436/25—Chemistry: analytical and immunological testing including sample preparation
  • Y10T436/25375—Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]

Definitions

• This invention relates to methods, compositions and kits for affinity isolation, affinity purification and affinity assay based on microbubbles coated with an affinity molecule.
• the field of isolating cells, virus, bacteria and soluble molecules has used various types of particles as a solid phase to absorb or bind to the target of interest.
• magnetic particles when coated with a ligand, such as an antibody, can bind to a target cell or soluble protein.
• the bound target on the magnetic particle effects a separation of the target from other cells types or proteins.
• the time required to bind the target cells or proteins is related to the surface area of the particles and the quantity of particles per unit volume of solution. The smaller the particle the more rapid the binding due to increased surface area. Unfortunately, greater surface area generally increases non-specific binding.
• Separation methods may, depending on the nature or principle of the separation, co-isolate different particles. This is apparent in separations based on gravity centrifugation in which particles and cells or other species may co-pellet. In addition some cell types such as macrophages and monocytes may themselves non-specifically ingest the particles and can be isolated along with the target cells. While individual limitations of the previous technology may be minimized or avoided by taking certain steps or precautions, certain limitations are inherent and cannot be entirely overcome. The fact that there are many different approaches with varying degrees of success suggests that a better solution to the problem is needed.
• the optimal separation agent would have an infinite surface area with zero non-specific interaction so that the binding would occur instantaneously and minimize binding to non-target cells or soluble molecules. Ideally, the agent should separate itself from the cell suspension or soluble molecule solution without entrapping non-target cells or molecules respectively.
• the present invention provides compositions for use in affinity isolation or affinity assay comprising microbubbles that are covalently coated with an affinity molecule.
• the microbubbles are protein microbubbles, such as albumin microbubbles.
• the protein microbubbles may be formed by the introduction of a gas into a solution of protein, for example, by sonication.
• gas may be introduced into the protein through a process comprising heating a solution of protein.
• the protein microbubbles may be stabilized, for example, by denaturing the protein or treatment with Cr+++.
• the affinity molecule may be directly coupled to the microbubble, for example, by using a heterobifunctional reagent such as sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate.
• the affinity molecule is indirectly coupled to the microbubble, such as through the interaction of at least one other molecule.
• the microbubble is directly coupled to streptavidin and the affinity molecule is biotinylated, such that the streptavidin and biotin interact to couple the affinity molecule to the microbubble.
• the affinity molecule may be directly coupled to the microbubble through an epoxy coating on the microbubble.
• the affinity molecule is coupled through an amine functional group on the microbubble.
• glass microbubbles are treated to generate reactive surface residues, which are in turn reacted with 3-aminopropyltriethoxy silane, generate amines.
• glass microbubbles are cis -diol coated and the affinity molecule is directly coupled to the glass through the cis -diol coating.
• the cis -diol coating can be generated, for example, by treating the glass microbubbles to generate reactive surface hydroxyl residues, reacting the hydroxyl residues with 3-glycidoxypropyltrimethoxysilane to generate epoxy functional residues, and treating the epoxy functional residues with acid to convert the epoxy function to cis -diol functions.
• the present invention also provides a method for generating protein microbubbles for use in affinity isolation or affinity assay.
• the method comprises heating a solution of protein.
• a solution of protein is treated ultrasonically to introduce gas into the solution, thereby generating protein microbubbles.
• the solution of protein is treated mechanically in the presence of a gas or a gas mixture.
• the gas is air and the protein is albumin.
• the protein microbubbles may be stabilized, for example by treatment with Cr +++ .
• the present invention also provides a method for generating microbubbles for use in affinity isolation or affinity assay comprising providing microbubbles; and coating the microbubbles with an affinity molecule.
• the species is a receptor, a ligand, or an antigen.
• the species is an analyte.
• the species is a virus or a cell.
• Standard techniques may be used for chemical syntheses, chemical modifications, chemical analyses, pharmaceutical preparation, formulation, delivery, and treatment of patients. Standard techniques may be used for recombinant DNA methodology, oligonucleotide synthesis, tissue culture and the like. Reactions and purification techniques may be performed e.g., using kits according to manufacturer's specifications, as commonly accomplished in the art or as described herein.
• Bubble refers to a small, hollow and lightweight globule, typically a small spherical volume of gas encased within a thin film. Bubbles can be filled with any gas, including, but not limited to oxygen, nitrogen, carbon dioxide, helium, fluorocarbon gases and various combinations thereof, such as air.
• the thin film may be any material that can encase a small volume of gas, such as an insoluble protein or lipid; a polymeric or non polymeric material; a solid such as a metal; a solid glass, ceramic or similar material; or a plastic, such as polystyrene, polyethylene, polypropylene, nylon, etc.
• the thin film is albumin.
• the thin film is borosilicate glass.
• the thin film is stable under the conditions and solutions it is exposed to.
• the bubble can be selectively burst, crushed or solubilized. "Microbubbles" are small bubbles, generally in the range of 0.1 to100 microns, typically 1 to 50, and frequently 2 to 20 or 2 to 30 microns in diameter.
• analyte refers to any substance that it is desirable to detect in an assay, and which may be present in a sample.
• the analyte can be, without limitation, any substance.
• an analyte comprises a substance for which there exists a naturally occurring antibody or for which an antibody can be prepared.
• the analyte may, for example, be a protein, a polypeptide, a hapten, a carbohydrate, a lipid, a drug, a cell, a cellular subcomponent or organelle (e.g., lysozomes, mitochondria) or any other of a wide variety of biological or non-biological molecules, complexes or combinations thereof.
• the analyte is an antibody.
• the analyte is a nucleic acid (DNA, RNA, PNA and nucleic acids that are mixtures thereof or that include nucleotide derivatives or analogs)
• Polyvalent ligand analytes that can be detected using compositions, methods and kits of the present invention will normally be poly(amino acids), i.e., polypeptides and proteins, polysaccharides, nucleic acids, and combinations thereof. Such combinations include components of cells, tissues, bacteria, viruses, cell walls, cell membranes, cellular organelles, chromosomes, genes, mitochondria, nuclei and the like. According to one aspect of the invention, certain analytes do not contain nucleic acid.
• protein analytes may be advantageously detected using the methods of the present invention.
• Such protein analytes can be classified according to family, with each family having similar structural features, biological functions, relationship to specific microorganisms (particularly disease causing microorganisms), and the like.
• Protein families of particular interest for the present invention include, for example, immunoglobulins, cytokines, enzymes, hormones, cancer antigens, nutritional markers, tissue specific antigens, and biowarfare agents.
• These protein analytes may be present in blood, serum, plasma, spinal fluid, synovial fluid, saliva, urine, semen, prosthetic fluid, cells or tissues.
• compositions, methods and kits of the present invention are clinically important proteins found in human plasma that may be detected using the compositions, methods and kits of the present invention:
• Important blood clotting factors that may be detected using the compositions, methods and kits of the present invention include the examples listed in the Table below.
• Table 1 BLOOD CLOTTING FACTORS International Designation Name I Fibrinogen II Prothrombin IIa Thrombin III Tissue thromboplastin V and VI Proaccelerin, accelerator globulin VII Proconvertin VIII Antihemophilic globulin (AHG) IX Christmas factor plasma thromboplastin component (PTC) X Stuart-Prower factor, autoprothrombin III XI Plasma thromboplastin XIII Fibrin-stabilizing factor
• compositions, methods and kits of the present invention include:
• Bacteria and viruses are also analytes that may be detected using the compositions, methods and kits of the present invention. Included among these biological analytes are, among others:
• the endogenous cells of a human patient are analytes that may be advantageously detected using the compositions, methods and kits of the present invention.
• the affinity molecules of the present invention need not comprise an entire naturally occurring molecule but may consist of only a portion, fragment or subunit of a naturally or non-naturally occurring molecule, as for example the Fab fragment of an antibody.
• the affinity molecule may further comprise a marker that can be detected.
• binding and “specific binding” as used herein is meant that an antibody or other molecule, especially an affinity molecule of the invention, binds to a target such as an antigen, ligand or other analyte, with greater affinity than it binds to other molecules under the specified conditions of the present invention.
• Antibodies or antibody fragments as known in the art, are polypeptide molecules that contain regions that can bind other molecules, such as antigens.
• “specifically binding” may mean that an antibody or other affinity molecule, binds to a target analyte molecule with at least about a 10 6 -fold greater affinity, preferably at least about a 10 7 -fold greater affinity, more preferably at least about a 10 8 -fold greater affinity, and most preferably at least about a 10 9 -fold greater affinity than it binds molecules unrelated to the target molecule.
• specific binding refers to affinities in the range of about 10 6 -fold to about 10 9 -fold greater than non-specific binding. In some embodiments, specific binding may be characterized by affinities greater than 10 9 -fold over non-specific binding.
• Polyclonal Antibodies are heterogeneous populations of antibody molecules derived from the sera of animals immunized with an antigen, or an antigenic functional derivative thereof.
• host animals such as rabbits, mice and goats, may be immunized by injection with an antigen or hapten-carrier conjugate, optionally supplemented with adjuvants.
• Polyclonal antibodies may be unpurified, purified or partially purified from other species in an antiserum.
• “Monoclonal antibodies,” or “Mabs”, which are homogeneous populations of antibodies to a particular antigen, may be obtained by any technique that provides for the production of antibody molecules, such as by continuous culture of cell lines. These techniques include, but are not limited to the hybridoma technique of Köhler and Milstein, Nature, 256:495-7 (1975 ); and U.S. Patent No. 4,376,110 ), the human B-cell hybridoma technique ( Kosbor, et al., Immunology Today, 4:72 (1983 ); Cote, et al., Proc. Natl. Acad. Sci.
• Such antibodies may be of any immunoglobulin class including IgG, IgM, IgE, IgA, IgD and any subclass thereof.
• the hybridoma producing the MAb of this invention may be cultivated in vitro or in vivo. Production of high titers of MAbs in vivo makes this a presently preferred method of production.
• chimeric antibodies Morrison, et al., Proc. Natl. Acad Sci., 81:6851-6855 (1984 ); Takeda, et al., Nature, 314:452-54 (1985 )) by splicing the genes from a mouse antibody molecule of appropriate antigen specificity together with genes from a human antibody molecule of appropriate biological activity can be used.
• a chimeric antibody can be a molecule in which different portions are derived from different animal species, such as those having a variable region derived from a murine MAb and a human immunoglobulin constant region.
• Antibody fragments that recognize specific epitopes may be generated by known techniques.
• such fragments include but are not limited to: the F(ab') 2 fragments that can be produced by pepsin digestion of the antibody molecule and the Fab fragments that can be generated by reducing the disulfide bridges of the F(ab') 2 fragments.
• Fab expression libraries may be constructed ( Huse, etal.,Science, 246:1275-81 (1989 )) to allow rapid and easy identification of monoclonal Fab fragments with the desired specificity.
• hapten refers to a small proteinaceous or non-protein antigenic determinant which is capable of being recognized by an antibody. Typically, haptens do not elicit antibody formation in an animal unless part of a larger species. For example, small peptide haptens are frequently coupled to a carrier protein such as keyhole limpet hemocyanin in order to generate an anti-hapten antibody response.
• Antigens are macromolecules capable of generating an antibody response in an animal and being recognized by the resulting antibody. Both antigens and haptens comprise at least one antigenic determinant or "epitope," which is the region of the antigen or hapten which binds to the antibody. Typically, the epitope on a hapten is the entire molecule.
• Receptor typically refers to a molecular structure within or on the surface a cell characterized by selective binding of a specific substance (e.g. a "ligand” ) and resulting in a specific physiologic effect that accompanies the binding.
• a specific substance e.g. a "ligand”
• receptors include cell surface receptors for peptide hormones, neurotransmitters, antigens, complement fragments and immunoglobulins and cytoplasmic receptors for steroid hormones.
• the receptor will typically be isolated and purified and need not effect or be capable of effecting a physiological or other biological effect.
• the methods of the present invention exploit the selective binding of the receptor to the specific substance.
• ligand refers generally to a molecule that binds to a receptor.
• a ligand is a small, soluble molecule, such as a hormone or neurotransmitter.
• solid support refers any solid phase that can be used to immobilize e.g., an analyte, an antibody or a complex.
• Suitable solid supports will be well known in the art and include the walls of wells of a reaction tray, such as a microtiter plate, the walls of test tubes, polystyrene beads, paramagnetic or non-magnetic beads, nitrocellulose membranes, nylon membranes, microparticles such as latex particles, and sheep (or other animal) red blood cells.
• Typical materials for solid supports include, but are not limited to, polyvinyl chloride (PVC), polystyrene, cellulose, nylon, latex and derivatives thereof.
• the solid support may be coated, derivatized or otherwise modified to promote adhesion of the desired molecules (e.g.,analytes) and/or to deter non-specific binding or other undesired interactions.
• desired molecules e.g.,analytes
• deter non-specific binding or other undesired interactions e.g., analytes
• the choice of a specific "solid phase" is usually not critical and can be selected by one skilled in the art depending on the assay employed.
• latex particles, microparticles, paramagnetic or non-magnetic beads, membranes, plastic tubes, walls of microtiter wells, glass or silicon chips, and red blood cells are all suitable sold supports.
• the solid support can be selected to accommodate various detection methods.
• 96 or 384 well plates can be used for assays that will be automated, for example by robotic workstations, and/or those that will be detected using, for example, a plate reader.
• the solid support may be a thin membrane, such as a nitrocellulose or nylon membrane.
• sandwich immunoassays the walls of the wells of a reaction tray are typically employed.
• paramagnetic beads may be used as a solid support. Suitable methods for immobilizing molecules on solid phases include ionic, hydrophobic, covalent interactions and the like, and combinations thereof.
• an additional receptor molecule can be any specific binding member which is immobilized upon (attached to) the solid phase and which has the ability to immobilize a capture reagent through a specific binding reaction.
• the additional receptor molecule enables indirect immobilization of the capture reagent to a solid phase before or during the performance of the assay.
• the solid phase thus can be a plastic, derivatized plastic, paramagnetic or non-magnetic metal, glass or silicon surface of a test tube, microtiter well, sheet, bead, microparticle, chip, or other configurations known to those of ordinary skill in the art.
• Protein generally refers to a short chain of amino acids linked by peptide bonds. Typically peptides comprise amino acid chains of about 2-100, more typically about 4-50, and most commonly about 6-20 amino acids. “Polypeptide” generally refers to individual straight or branched chain sequences of amino acids that are typically longer than peptides. “Polypeptides” usually comprise at least about 100 to 1000 amino acids in length, more typically at least about 150 to 600 amino acids, and frequently at least about 200 to about 500 amino acids. “Proteins” include single polypeptides as well as complexes of multiple polypeptide chains, which may be the same or different.
• peptides, polypeptides and proteins include, without limitation, biologically active and inactive forms; denatured and native forms; as well as variant, modified, truncated, hybrid, and chimeric forms thereof.
• the peptides, polypeptides and proteins of the present invention may be derived from any source or by any method, including, but not limited to extraction from naturally occurring tissues or other materials; recombinant production in host organisms such as bacteria, fungi, plant, insect or animal cells; and chemical synthesis using methods that will be well known to the skilled artisan.
• conjugate refers to two molecules that have been covalently attached, or otherwise linked together.
• a nucleic acid conjugate is generated by covalently linking a nucleic acid to a protein, polypeptide or other affinity molecule.
• the protein, polypeptide or other affinity molecule is covalently attached to a nucleic acid via a linking group to form a conjugate.
• a "kit” for detecting the presence of an analyte in a sample by the methods of the invention may, by way of example, comprise at least one container means having disposed therein a binding pair specific for the selected analyte.
• the kit may further comprise other containers comprising one or more of the following: buffers, solutions or other reagents and materials necessary for performing analyte detection; reagents capable of amplifying the nucleic acid probe components of the binding pairs; and reagents capable of detecting the presence of nucleic acid components following amplification.
• the kit further comprises instructions for use.
• the kit if intended for diagnostic use, may also include notification of a FDA approved use and instructions therefor.
• a compartmentalized kit includes any kit in which reagents are contained in separate containers.
• Such containers include small glass containers, plastic containers or strips of plastic or paper.
• Such containers allow the efficient transfer of reagents from one compartment to another compartment such that the samples and reagents are not cross-contaminated and the agents or solutions of each container can be added in a quantitative fashion from one compartment to another.
• Such containers may include a container which will accept a test sample, a container which contains the probe or primers used in the assay, containers which contain buffers and reagents (such as phosphate buffered saline, Tris-buffers, and the like), and containers which contain the reagents used to detect the marker nucleic acid, amplified product, or the like.
• buffers and reagents such as phosphate buffered saline, Tris-buffers, and the like
• containers which contain the reagents used to detect the marker nucleic acid, amplified product, or the like.
• a kit for coupling DNA to an antibody or other affinity molecule by the methods of the invention may comprise at least one container means having disposed therein the lyophilized activated DNA.
• the kit may further comprise other containers comprising one or more of the following: reagents, buffers and agents capable of detecting the presence of nucleic acid after the reaction.
• the kit further comprises instructions for use.
• a kit for making or using the novel compositions and methods for isolating and assaying analytes described herein may include the already manufactured microbubble or the thin film used to create the microbubble. Likewise, the microbubble of the kit may or may not already have the attached affinity molecule.
• the kit may further comprise other containers comprising one or more of the following: reagents, buffers and agents capable of making the microbubbles or useful in employing them for methods of affinity isolation, purification, concentration, etc..
• the kit further comprises instructions for use.
• compositions and methods described in the present invention can readily be incorporated into one of the established kit formats that are well known in the art.
• the present invention provides novel compositions and methods for isolating and assaying analytes, including also cells, viruses, cellular subcomponents and soluble molecules from solution. It relies on coated microbubbles to specifically bind the target analyte (cell, virus, cellular subcomponent or soluble molecule). According to the invention, microbubbles are coated with, or otherwise made to exhibit on their exterior surface, an affinity molecule.
• the novel compositions and methods of the present invention can also be used to concentrate analytes, including but not limited to antibodies, antigens, proteins and nucleic acids.
• the microbubbles are protein microbubbles, which can be comprised of any peptide, polypeptide, protein or combinations thereof. Both synthetic and naturally occurring peptides, polypeptides, proteins and combinations are contemplated by the invention.
• the protein microbubbles can be readily formed into microbubbles through the introduction of a gas.
• the protein is albumin.
• the protein microbubbles of the invention are typically formed by the introduction of a gas into a solution of protein, for example, by sonication.
• the bubbles can be filled with any gas, including, but not limited to oxygen, nitrogen, carbon dioxide, helium, fluorocarbon gases and various combinations thereof, such as air.
• gas may be introduced into the protein through a process comprising heating a solution of protein. Without being limited to a specific theory, heating may serve to stabilize the protein microbubbles by denaturing the protein.
• the protein microbubbles may be stabilized, for example, by denaturing the protein, fixing the protein, crosslinking the protein or treatment with Cr +++ .
• the microbubbles are stabilized by cross linking with aldehydes such as glutaraldehyde or formaldehyde.
• Coating of microbubbles with an affinity molecule can be accomplished by any method known in the art.
• proteins contain amine functional groups that can serve as the basis for numerous modifications and coupling reaction, such as reaction with aldehydes.
• the materials that make up microbubbles e.g. protein, glass and the like, can be chemically derivatized or functionalized to covalently interact with various types of affinity molecules.
• the skilled artisan will be familiar with a variety of commercial reagents, products and kits for coupling proteins and other molecules to the microbubbles of the invention.
• the affinity molecule may be directly coupled to the protein, for example, by using a heterobifunctional reagent such as sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate.
• the affinity molecule is indirectly coupled to the protein, such as through the interaction of at least one other molecule.
• microbubbles are directly coupled to streptavidin and the affinity molecule is biotinylated, such that the streptavidin and biotin interact to couple the affinity molecule to the protein.
• the interactions of biotin and avidin/streptavidin are well known in the art, as are methods for coupling these molecules to other species. Reference may also be made to a general or more specific textbook or laboratory manual describing the chemistry, biology, and interactions of biotin, avidin and streptavidin, and/or the methods for coupling biotin and avidin/streptavidin to other molecules. See e.g., Avidin-Biotin Chemistry:A Handbook (Savage, et. al., eds. Pierce Chemical Co., Rockford, IL,1992 )
• This streptavidin microbubble can then be easily coated with a biotinylated ligand such as a biotinylated antibody; alternatively epoxy coated glass micro bubbles can be reacted directly with ligands or coated directly or indirectly by methods known to those skilled in the art.
• a biotinylated ligand such as a biotinylated antibody
• the method comprises the steps of providing microbubbles coated with an affinity molecule in a solution, contacting the microbubbles with a species that interacts with the affinity molecule in a solution, thereby generating microbubbles coated with the species, and separating the microbubbles coated with the species from the solution ⁇ in a preferred embodiment, allowing the microbubbles coated with the species to float to the top of the solution ⁇ thereby separating the species from the solution.
• proteins antigen, antibodies, ligands, receptors, hormones
• nucleic acids lipoproteins, fats, triglycerides
• sugars carbohydrates
• viruses cells, cellular components, subcellular organelles, and components of subcellular organelles, as well as complexes thereof
• the method comprises the steps of providing microbubbles coated with an affinity molecule in a solution, contacting the microbubbles with a species that interacts with the affinity molecule in a solution, thereby generating microbubbles coated with the species, and separating the microbubbles coated with the species from the solution ⁇ in a preferred embodiment, allowing the microbubbles coated with the species to float to the top of the solution ⁇ thereby separating the species from the solution.
• the species that can be isolated, assayed, purified or concentrated can be any manner of material including proteins (antigen, antibodies, ligands, receptors, hormones), nucleic acids (RNA, DNA nucleotide analogs, mixtures thereof, etc), lipoproteins, fats, triglycerides, sugars, carbohydrates, viruses, cells, cellular components (liposomes, endoplasmic reticulum, etc.), subcellular organelles (mitochondria, etc.), and components of subcellular organelles, as well as complexes thereof.
• the species is a receptor, a ligand, or an antigen.
• the species is an analyte.
• the species is a virus or a cell.
• the coated microbubbles of the invention bind to the target species, including cells, viruses, analytes or other molecules and then rise to the surface of the solution, thus separating themselves from the contacting solution and non-target species.
• the solution containing the microbubbles may be centrifuged or subjected to a bubble trap to further effect the separation more rapidly.
• the albumin microbubbles of the invention have the useful property of being able to be easily destroyed and made to visually disappear by applying pressure or vacuum to the solution, or by adding a small amount of a detergent or surfactant.
• This aspect of the invention is particularly useful where it is desirable to isolate the target species devoid of the capturing microbubble. For example, it may be desirable to characterize the phenotype of an affinity-isolated cell or to free the isolated cell for further analysis or propagation.
• the methods of the present invention provide, in some embodiments, a simple means for releasing the species from the capturing microbubble that avoids potentially damaging reagents, such as enzymes, harsh chemicals and extremes of pH. In other embodiments, the analyte or species may be released from the microbubble by enzymatic or chemical means.
• Glass microbubbles advantageously can be constructed from borosilicate glass which is largely free of contaminating material. This material is also resistant to breakage or destruction during normal handling.
• the present invention also provides methods for generating microbubbles for use in affinity isolation or affinity assay comprising providing microbubbles; and coating the microbubbles with an affinity molecule.
• Albumin solution (Human) 5%, USP (Bayer Corporation, Elkhart, IN) was diluted to 1%with air-saturated normal saline at room temperature. Twenty milliliters of the diluted solution was placed into a 50 ml glass beaker and immersed in a 85°C water bath below the 25 ml level on the beaker. The temperature of the albumin solution was monitored using digital thermometer with gentle stirring of the solution. At a process temperature of 73°C, the probe of a Branson Digital Sonifier ® ,Model 450 (Branson Ultrasonics Corp., Danbury, CT) was placed in contact with the surface of the albumin solution and immediately sonicated at 80% amplitude for 10 seconds.
• Branson Digital Sonifier ® ,Model 450 Branson Ultrasonics Corp., Danbury, CT
• the beaker was removed from the water bath, placed in crushed ice, and stirred gently until the temperature was reduced to 40° C.
• the albumin microbubble suspension was transferred to a 150 ml flexible carboy (Flexboy R Bag, Stedim, Concord, CA) at room temperature. The process was repeated several times with fresh solution until the bag was filled.
• the microbubble suspension was adjusted to 0.05% sodium azide and the bag stored vertically under refrigeration for at least 24 hours. The sonication process converted approximately 5% of the soluble albumin to insoluble, air-filled albumin microbubbles.
• Example2 Preparation of Chromium-stabilized Albumin Microbubbles.
• Unconverted albumin solution was drained away from underneath the floating layer of microbubbles and replaced by cold, air-saturated phosphate buffered saline, pH 7.4 (PBS), containing 0.2 % polyvinyl alcohol (MW 30,000-70,000)(PVA/PBS).
• PBS cold, air-saturated phosphate buffered saline, pH 7.4
• PVA/PBS polyvinyl alcohol
• the microbubbles were washed free of residual soluble albumin by repeated centrifugation at 200 x g, at 4°C for 5 min, draining, and replenisment of the solution with fresh cold, air-saturated PVA/PBS.
• the washed albumin microbubbles were suspended at approximately 25% v/v in PVA/PBS and biotinylated by reaction with sulfosuccinimidyl-6-(biotinamido) hexanoate (sulfo-NHS-LC-biotin; EZ-LinkTM sulfo-NHS-LC-biotin, Pierce Biotechnology, Inc., Rockford, IL) at a concentration of 0.01 to 1.0 mg/ml under gentle agitation at room temperature for at least one hour.
• biotin on the surface of the albumin microbubbles was confirmed by observing the spontaneous association of biotin-microbubbles with BioMag Nuclease Free Streptavidin paramagnetic particles (Polysciences, Inc., Warrington, PA) in suspension.
• BioMag Nuclease Free Streptavidin paramagnetic particles Polysciences, Inc., Warrington, PA
• the biotin-coated albumin microbubbles were stored under refrigeration in PVA/PBS containing 0.05% sodium azide.
• Air-filled albumin microbubbles were coated with streptavidin (Prozyme, San Leandro, CA) indirectly by exposing biotin-microbubbles to an excess of streptavidin. Under these conditions, cross-linking of microbubbles is avoided. Streptavidin was also coated onto albumin microbubbles directly via a bifunctional protein cross-linking reagent.
• albumin microbubbles were coated directly with streptavidin using sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (s-SMCC).
• Streptavidin at 10 mg/ml in PBS, pH 7.4, was treated with a 5 to 10-fold molar excess of n-succinimidyl S-acetylthioacetate (SATA) for at least 1hour at room temperature. Unreacted SATA was removed from the streptavidin by FPLC using a Sephadex G-25 resin equilibrated in PBS, and the purified protein was stored frozen.
• the protective acetyl group was removed from the modified streptavidin by treatment with PBS containing 50 mM hydroxylamine and 2.5 mM EDTA, pH 7.5, for 2 hours at room temperature.
• PBS containing 50 mM hydroxylamine and 2.5 mM EDTA, pH 7.5
• a suspension of albumin microbubbles suspended in PVA/PBS was treated with 0.01 to 1 mg/ml s-SMCC under gentle agitation for 30 min at room temperature.
• Excess s-SMCC reagent was immediately removed by centrifugal washing (repeated 4 times), and the s-SMCC microbubbles were combined with the sulfhydryl-modified streptavidin.
• the streptavidin becomes covalently coupled to the surface of the albumin microbubbles by reaction of the maleimide functional group with the freshly exposed streptavidin sulfhydryl group.
• the microbubbles were washed free of excess streptavidin by repeated centrifugal washings, suspended in cold, air-saturated PBS containing 0.05% sodium azide and stored under refrigeration.
• Example 5 Coating Albumin Microbubbles with Antibody.
• Affinity-purified antibody to E. coli 0157:H7 was obtained from KPL (Gaithersburg, MD) and biotinylated as described below.
• the antibody was dissolved in PBS, pH 7.4 and warmed to 37° C for 30 min.
• the warmed solution was treated with an 8-12 fold molar excess of sulfosuccinimidyl-6-(biotinamido) hexanoate (EZ-Link TM sulfo-NHS-LC-biotin) for 2 hrs at room temperature.
• EZ-Link TM sulfo-NHS-LC-biotin Excess biotin reagent was removed by G-25 Sephadex gel filtration chromatography, eluting with PBS.
• the biotinylated antibody was concentrated by ultra-filtration using a Microcon ® YM-30 Filter Device (Millipore, Bedford, MA) and stored under refrigeration in the presence of sodium azide as preservative.
• Avidin-coated albumin microbubbles were resuspended by gentle agitation and combined with a molar excess of biotin-labeled antibody in PBS. Excess material was removed from the insoluble microbubbles by repeated centrifugation and resuspension as described above.
• the antibody-coated albumin microbubbles were stored in PVA/PBS containing sodium azide, at 4° C.
• Example 6 Capture of Bacterial Cells on Antibody-Coated Microbubbles.
• E. coli 0157:H7 was obtained from American Type Culture Collection (Manassas, VA) and propagated on Luria Bertani (LB) liquid and agar media at 37° C. Bacteria grown in liquid media were serially diluted in cold, sterile PVA/PBS or PBS containing 0.2 % BSA (BSA/PBS) to a density of approximately 5,000 cells/ml. One-tenth volume of microbubble suspension was added to the cell suspension and gently agitated for several minutes at room temperature. The microbubbles were allowed to float to the surface of the mixture by natural buoyancy over 10 minutes.
• Example 7 Preparation of Microbubbles By First Modifing Albumin followeded by Sonication.
• Bovine Serum Albumin (BSA; Bovuminar Cohn Fraction V, Intergen, Purchase, NY) was dissolved in normal saline, containing 4 mM sodium caprylate and 4 mM sodium tryptophanate to 50 mg/ml,sterile filtered and stored in a clear glass container, under fluorescent lighting at room temperature for two weeks. This treatment photo-oxidized free sulfhydryl groups that can interfere with microbubble formation. Twenty milliliters of the BSA solution was removed and adjusted to pH 8.5 with 1 M NaOH.
• s-NHS-LC-biotin Twenty-five micrograms of s-NHS-LC-biotin was added with mixing and the pH maintained at 8.5 for 1 hour at room temperature. The reaction was diluted to 1% albumin by the addition of normal saline and subjected to the sonication process as described above for unmodified human albumin. The resulting albumin microbubbles were washed several times with 1% BSA in normal saline to remove unincorporated biotin. The microbubbles prepared from biotinylated albumin were reactive with avidin or streptavidin and could be coated with avidin or streptavidin as described above.
• 3MTM ScotchLiteTMGlass Bubbles S60HS (St Paul, MN), having a density of about 0.6 g/cc and an average diameter of about 30 ⁇ m, were suspended in water and allowed to float to the top of the suspension. The liquid layer was drained from the bottom to remove fines and shards. This was conveniently performed in a 60 cc disposable syringe fitted with a stopcock mounted on the tip. The washing was repeated several times. Reactive surface hydroxyl residues were provided by suspension of the washed microbubbles in 0.25 M NaOH for 24 hours at 60° C, followed by washing with water to remove the alkali. The microbubbles were subsequently treated with 0.05 M HC1for 1 hour at room temperature.
• the glass microbubbles were suspended in 70% sulfuric acid and 9% hydrogen peroxide for 16 hours at room temperature, followed by exhaustive washing with water.
• the acid-treated microbubbles were resuspended in a solution of 3-APS:water:ethanol (3:4:92 by volume) prepared just prior to use. The reaction was allowed to proceed for 30 minutes at room temperature. Excess reagent was removed by washing in ethanol, and the glass microbubbles baked at 115°C for 1 hour. The microbubbles were washed again in ethanol and oven dried at 60° C.
• Amine-coated glass microbubbles were stored dry at room temperature. The presence of functional surface amine groups at 2.5-3.0/nm 2 was confirmed by analysis using s-succinimidyl-4-O-(4,4'dimethoxytrityl) butyrate (Pierce).
• Amine-coated glass microbubbles were suspended in 50 mM sodium bicarbonate, 0.1% TweenTM20, pH 8.5, and reacted with sulfo-NHS-LC-biotin for two hours at room temperature.
• the biotin reagent was present at a 0.1 to 7-fold excess over available surface amines.
• the glass microbubbles were washed and stored in PBS containing 0.1% TweenTM20 (PBS/Tween)TM.
• Avidin dissolved in water at 5 mg/ml, was added in molar excess to saturate the available biotin sites. Excess avidin was removed by washing with PBS/TweenTM and the microbubbles were stored in PBS, containing 0.2% BSA (BSA/PBS) and 0.05% sodium azide, under refrigeration.
• Amine glass microbubbles were also coated with sulfhydryl-modified avidin via s-SMCC cross-linking reagent.
• Amine glass microbubbles were suspended 1:10 (w/v) in 50 mM sodium phosphate, pH 7.5 containing 10% dimethyl formamide and 2 mg/ml s-SMCC for one hour at room temperature.
• the maleimide-coated glass bubbles were washed with 100% dry ethanol, drained, dried under vacuum in a glass vial, and stored under nitrogen at -20° C.
• Example 10 Capture of E. coli 0157 Onto Antibody-Coated Glass Microbubbles:
• E. coli grown in culture was serially diluted in cold, sterile PBS containing BSA and sodium azide to 5,000 cell/ml.
• the bacterial suspension was treated with 1% (v/w) antibody-coated microbubbles with agitation at room temperature for several minutes.
• the microbubbles were allowed to float to the surface and 10 ⁇ l of underlying liquid layer (cleared by floatation of the microbubbles) was removed and plated onto agar media in parallel with untreated, control samples of bacterial suspension.
• Bacterial suspensions treated with uncoated microbubbles exhibited no reduction in colonies formed overnight at 37° C.
• Bacterial suspension treated with antibody-coated glass microbubbles exhibit a 50 to 100% decrease in colony forming units, which were recovered by resuspension and plating. This result confirmed the capture of bacterial cells on glass microbubbles coated with a specific antibody.
• a 25% suspension of cis -diol-coated glass microbubbles was activated with 0.3 M carbonyl diimidizole (CDI) in dry acetone for 1 hour at room temperature in a sealed vessel, with venting every 10 minutes. Excess reagent was removed by washing with dry acetone and the glass microbubbles were dried under vacuum at room temperature. The activated microbubbles were stored dry under nitrogen at 4° C.
• CDI carbonyl diimidizole
• CDI-activated glass microbubbles were coated by overnight incubation with 4 mg/ml avidin dissolved in 0.1 M sodium carbonate, pH 9.5 at room temperature. The pH was reduced to 6.5 by the addition of 0.2 M sodium phosphate, monobasic. The avidin-coated glass microbubbles were washed and stored in BSA/PBS containing sodium azide.
• Biotin-labeled antibody to E. coli 0157:H7 was applied and bacteria removed from suspension as previously described above. This experiment gave a 50-100% reduction in bacteria, as evidenced by a reduced number of colonies relative to control samples.

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